The present invention concerns a low-leakage pot magnet sytem for moving-coil loudspeakers.
In such low-leakage magnet systems, which are especially suitable for use in television sets or in the vicinity of ferrite antennae, the magnetic leakage field at 100 mm distance from the center of the pole core or from the bottom of the screen pot is less than 1 A/cm, while barium ferrite and AlNiCo systems of equal size have leakage fields on the order of 5 A/cm.
Due to the high price of such sytems, numerous attempts have been made to reduce the external leakage through less expensive measures. In one embodiment, for example, the loudspeaker magnet enclosure, or pot, made of iron is extended downwardly and the magnet system is inserted into it. The screening effect is, however, not very strong. A design in which the magnet system is located within the diaphragm cone itself is more effective. This design has the additional advantage of small overall height. The manufactures of television sets occasionally compensate for the influence of the loudspeaker system by gluing small ferrite magnets to the picture tube itself. However, this requires an additional expenditure during the manufacturing process.